You need to change the uptime script so it sets the uptime (if present) to a variable (e.g %uptime), and also have it unset %uptime and %target at the beginning.
Then I imagine you would need something like this
on *:connect:{ timer1 0 30 streamcheck }
alias -l streamcheck {
uptime
if ( %uptime ) && (%target = YourChannelName) {
timer1 off
timer2 0 30 msg # text goes here
}
}
But you should make it say different lines. Getting spammed with the same timed message is pretty obnoxious :p